Whisk yogurt, mayonnaise, lemon juice, honey, Dijon, salt, and pepper in a large bowl until smooth.
Core and dice the apples. Add them to the bowl and gently toss to coat.
Fold in celery, walnuts, cranberries, and parsley until everything is evenly dressed.
Taste and adjust seasoning, adding a pinch of salt or a splash of lemon if needed.
Serve right away or chill briefly. Spoon over lettuce leaves if using.